Ability of Nonenzymic Nitration or Acetylation of E. coli Glutamine Synthetase to Produce Effects Analogous to Enzymic Adenylylation
AUTOR(ES)
Cimino, Filiberto
RESUMO
Treatment of unadenylylated glutamine synthetase from Escherichia coli with tetranitromethane or with N-acetylimidazole produces alterations in catalytic parameters that are similar to alterations caused by the physiologically important process of adenylylation. All three modification reactions lead to a change in divalent ion requirement for biosynthetic activity; the unmodified enzyme requires Mg2+ for activity, whereas the modified enzymes exhibit increased activity with Mn2+. The γ-glutamyl transferase activity of the modified enzyme is more sensitive to feedback inhibition by tryptophan, histidine, CTP, and AMP, and to inhibition by Mg2+ or to inactivation by 5 M urea. Finally, the pH optimum for the unmodified enzyme is 7.9, while the modified enzymes are more active at pH 6.8.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=283082Documentos Relacionados
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